Ancient humans hunted mammoths, which some think contributed to their extinction. (Source: On Charcoal)

Researchers in a new study claim that the extinctions, possibly triggered by man, caused the birch trees to take over in regions of Siberia, causing a warming effect of as much as 1 degree Fahrenheit. (Source: EW Birch Builders)

Mammoth extinction 10,000 years ago may have led to as much as a 1 degree Fahrenheit increase in temperatures

Christopher
Doughty, a post-doctoral researcher at the Carnegie Institution for
Science in Stanford, California, has led a team of researchers that
has reached some controversial and unusual claims about mankind's
role in changing
the Earth's climate.

Doughty, in a paper published [PDF]
in the journal Geophysical
Research Letters,
claims that the extinction of woolly
mammoths may have triggered a cascade of effects warming
Siberia and neighboring Beringia by at least 0.3 to 0.4 degrees
Fahrenheit. If these controversial claims prove true, it would
likely be the first example of man influencing the world's climate in
humanity's brief history as a species.

The report may change
preconceptions about climate change, claims
Doughty; "Some people say that people are unable to affect
the climate, that it's just too big. That's obviously not the
case. People started to affect global climate much earlier than we
thought."

Previous studies had indicated that mankind's
development of agriculture 8,000 years ago could have changed the
Earth's climate, but the effects of hunting in mankind's earlier days
were not thought to have had significant impact. The new study
draws its basis from a previous
study in the November 20, 2009 edition of the
journal Science.
That study indicated that mammoths kept small trees in check,
preserving grasslands. With their extinction, the darker trees
grew, increasing the overall darkness of the terrain, absorbing more
solar radiation, and ultimately triggering a warming effect.

The
issue with that study was that it posed a chicken-and-the-egg sort of
conundrum; warming climates would encourage tree growth over tundra
grasslands, but tree growth could also trigger
warming.
Doughty claims in his new study that in the 850-year period where
most of the mammoths disappeared from hunting, the levels of birch
pollen increased by 26 percent. Using modern elephant data, it
was estimated that 23 percent of this increase came from the death of
the mammoths, while the rest was caused by the heating trend
itself.

The team then compiled vegetation loss findings and
climate simulations to pinpoint how much of an impact the forestation
increased had. They found that it likely raised temperatures
from 0.4 degrees F to the nearly 1 degree F.

Doughty admits in
the study that it's not been conclusively shown that humans caused
the extinction of mammoths in the first place (again, this is a
chicken-egg riddle as warming climates could have pushed them to
extinction, but their extinction could have warmed climates).
Man did hunt the beasts, and its the prevailing theory that we played
at least a small role in their extinction.

The study was
funded by NASA and the Carnegie Institution for Science.

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